Typically, samples of bodily fluids such as serum, plasma, urine, and the like, are assayed for the presence of analytes such as drugs, viruses, or bacteria by reacting the samples according to a specific test protocol with specific reagents which are selected to identify a particular analyte. The protocol specifies the sequence in which sample and reagents are to be introduced, the timing for the introduction of sample and reagents, the volumes of each to be used, and other conditions to be controlled, such as temperature. The resulting reaction mixture is typically allowed to incubate for a predetermined time and is then read, optically or otherwise, to determine the presence and concentration of the specific analyte which the assay is designed to identify. In general, processes and apparatuses for preparing and reading immunoassays are well known.
Automated clinical analyzers are capable of performing immunoassays on an entire batch of samples simultaneously. In some types of known analyzers, such as the well-known TDx.RTM. Clinical Analyzer manufactured by Abbott Laboratories of North Chicago, Ill., a batch of sample containers are mounted radially about a rotatable carousel together with a corresponding number of reaction containers. The carousel is then mounted inside the analyzer. Inside the analyzer, the carousel rotates stepwise to move each corresponding sample container and reaction container pair first to a position adjacent a preparation station, and then to a second position adjacent a reading station. A mechanical apparatus having pipetting means and typically operating under program control is located in proximity to the preparation station. Also located in proximity to the preparation station are a plurality of reagent containers which contain the reagents required to perform a specific immunoassay on the batch of samples contained in the sample containers. The reagent containers may be individual containers or may be configured as an integrated pack.
At the preparation station, the mechanical apparatus and pipetting means operate to access and transfer volumes of sample from a sample container and reagents from the reagent containers into a reaction container according to the protocol established for the specific assay. When the mechanical apparatus completes the preparation of the reaction mixture according to the test protocol, the carousel rotates, positioning the next corresponding sample container and reaction container pair adjacent the preparation station, and moving the previous pair toward the reading station. Known carousels typically hold between 20 and 25 containers.
One limitation of a number of these analyzers is that they are capable of performing only one assay at a time on each batch of samples on the carousel. In order to perform a different assay, it is necessary to physically remove the reagent containers either individually or as a pack from the analyzer and replace them with different reagent containers or a different pack for the assay to be run. The requirement of changing reagent packs for each assay has an adverse impact on the throughput of the analyzer. Where multiple assays are to be performed on the same batch of samples or on different samples, the requirement of changing reagent containers for each assay has an even more severe adverse impact on the throughput of the system. Decreased throughput increases both the time and cost associated with such assays.
One approach to solving this problem of some known analyzers has been to provide unit dose or unitized reagent containers each containing an aliquot or reagents sufficient to carry out a specific assay on one sample. These containers are mounted on the analyzer carousel in positions corresponding to each sample container. With utilized reagent containers, different immunoassays can be carried out on each sample. For example, one sample can be assayed for a certain class of drugs, the next for the presence of a strain of virus, the next for a certain class of bacteria, and so forth.
The unit dose approach has not provided a completely satisfactory solution to the problems of the prior art. First, it is relatively expensive to manufacture and use unit dose containers, which are limited to use with one sample. Second, it is time consuming. This drawback is particularly noticeable where only one or a small number of different assays are to be conducted on the samples in a particular batch. With the relatively large number of sample and unit dose reagent containers that must be mounted on each carousel, the risk of inaccurate delivery of a sample to a specific unitized reagent container is increased. This increases the risk of performing the wrong test on a sample.
In view of the foregoing limitations and drawbacks of the prior art, it is the primary objective of the present invention to provide a multiple dose reagent pack which can be expediently mounted on a carousel with a plurality of sample containers to provide reagents for conducting immunoassays of a plurality of such samples. It is a related object to provide a carousel which is adapted to hold a plurality of such multiple dose reagent packs interspersed with such sample containers to flexibly provide reagents for performing the same or different assays on the same or different samples. It is a significant advantage of the invention that flexibility is provided to perform a selected plurality of different assays on the same or different samples and to selectably vary the number of different assays performed on each sample while maintaining high throughput levels and reducing the requirement for physical interaction with the analyzer and the carousel.